Table 3. Key structural features and predicted non-aqua transport substrates of putative barley aquaporin proteins.
| Barley AQP | NPA motif | Ar/R selectivity filter | P1—P5 | Subcellular location | Predicted transport substrate a | Rice ortholog (% identity)* |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| LB/LE | TM2 | TM5 | LE1 | LE2 | P1 | P2 | P3 | P4 | P5 | cDNA | Protein | |||
| PIPs | ||||||||||||||
| HvPIP1;1 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO2, urea | OsPIP1;2 (89.6) | OsPIP1;1 (92.3) |
| HvPIP1;2 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO2, urea, water 8 | OsPIP1;3 (85.7) | OsPIP1;3 (89.3) |
| HvPIP1;3 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron 1, CO2, urea | OsPIP1;3 (82.8) | OsPIP1;3 (88.0) |
| HvPIP1;4 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron 1, CO2, urea | OsPIP1;3 (83.2) | OsPIP1;3 (88.6) |
| HvPIP1;5 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO2, urea | OsPIP1;1 (92.3) | OsPIP1;1 (94.1) |
| HvPIP2;1 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO 2 2; 5, urea, water 7 | OsPIP2;2 (87.5) | OsPIP2;2 (88.2) |
| HvPIP2;2 | NPA/ NPA | F | H | T | R | M | S | A | F | W | PM | CO 2 5, glycerol, urea, water 7; 8 | OsPIP2;1 (78.0) | OsPIP2;1 (72.2) |
| HvPIP2;2a | NPA/ NPA | F | H | T | R | M | S | A | Y | L | PM | glycerol, urea | OsPIP2;6 (78.3) | OsPIP2;6 (75.5) |
| HvPIP2;3 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO 2 5, urea, water 7 | OsPIP2;3 (90.2) | OsPIP2;3 (89.3) |
| HvPIP2;4 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, urea, water 7 | OsPIP2;3 (90.1) | OsPIP2;3 (88.3) |
| HvPIP2;5 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO2 5, urea, water7; 8 | OsPIP2;1 (90.1) | OsPIP2;1 (90.0) |
| HvPIP2;6 | NPA/ NPA | F | H | T | R | Q | S | A | F | W | PM | boron, CO2, urea | OsPIP2;4 (51.6) | OsPIP2;4 (51.0) |
| HvPIP2;7 | NPA/ NPA | F | H | T | R | A | S | A | F | W | PM | CO2, water 8 | OsPIP2;7 (75.0) | OsPIP2;7 (77.4) |
| HvPIP2;7a | - | F | - | - | - | - | - | - | - | - | - | - | OsPIP2;7 (48.5) | OsPIP2;7 (44.1) |
| HvPIP2;8 | NPA/ NPA | F | H | T | R | H | S | A | F | W | PM | - | OsPIP2;5 (71.0) | OsPIP2;5 (68.0) |
| HvPIP2;9 | NPA/ NPA | F | H | T | R | H | S | A | F | W | PM | - | OsPIP2;5 (68.3) | OsPIP2;5 (63.0) |
| HvPIP2;10 | NPA/ NPA | F | H | T | R | M | S | A | F | W | PM | CO2, glycerol, urea | OsPIP2;7 (76.9) | OsPIP2;7 (63.8) |
| HvPIP2;11 | NPA/ NPA | F | H | T | R | H | S | A | F | W | PM | - | OsPIP2;1 (68.3) | OsPIP2;3 (66.4) |
| HvPIP2;12 | NPA/ NPA | F | H | T | R | H | S | A | F | W | PM | - | OsPIP2;1 (74.2) | OsPIP2;1 (70.0) |
| TIPs | ||||||||||||||
| HvTIP1;1 | NPA/ NPA | H | I | A | V | T | S | A | Y | W | PM/V | H2O2, urea, water 8 | OsTIP1;1 (89.3) | OsTIP1;1 (89.6) |
| HvTIP1;2 | NPA/ NPA | H | I | A | V | T | S | A | Y | W | V | H2O2, urea, water 8 | OsTIP1;2 (87.3) | OsTIP1;2 (90.8) |
| HvTIP2;1 | NPA/ NPA | H | I | G | R | T | S | A | Y | W | V/PM | ammonia, formamide, H2O2 | OsTIP2;1 (89.3) | OsTIP2;1 (90.7) |
| HvTIP2;2 | NPA/ NPA | H | I | G | R | T | S | A | Y | W | PM | ammonia, formamide, H2O2 | OsTIP2;1 (68.6) | OsTIP2;1 (88.3) |
| HvTIP2;3 | NPA/ NPA | H | I | G | R | T | S | A | Y | W | V/PM | ammonia, formamide, H2O2, water 8 | OsTIP2;2 (91.2) | OsTIP2;2 (90.7) |
| HvTIP3;1 | NPA/ NPA | H | I | A | R | T | V | A | Y | W | PM/M | H2O2 | OsTIP3;1 (88.0) | OsTIP3;1 (88.3) |
| HvTIP3;2 | NPA/ NPA | H | I | A | R | S | A | A | Y | W | Chl | H2O2 | OsTIP3;2 (84.1) | OsTIP3;2 (81.3) |
| HvTIP4;1 | NPA/ NPA | Q | T | A | R | T | S | A | Y | W | V/PM | - | OsTIP4;1 (81.1) | OsTIP4;1 (80.9) |
| HvTIP4;2 | NPA/ NPA | H | T | A | R | T | S | A | Y | W | V/PM | glycerol, urea | OsTIP4;2 (75.0) | OsTIP4;2 (70.2) |
| HvTIP4;3 | NPA/ NPA | H | T | A | R | A | S | A | Y | W | PM | - | OsTIP4;3 (63.7) | OsTIP4;3 (52.8) |
| HvTIP5;1 | NPA/ NPA | Q | V | A | R | S | S | A | Y | W | Chl | - | OsTIP5;1 (86.1) | OsTIP5;1 (79.2) |
| NIPs | ||||||||||||||
| HvNIP1;1 | NPA/ NPA | W | V | A | R | F | T | A | Y | V | PM | Glycerol, water 6 | OsNIP1;1 (83.1) | OsNIP1;1 (84.9) |
| HvNIP1;2 | NPA/ NPA | W | V | A | R | F | T | A | Y | I | PM | glycerol, arsenite 6 , water 6 | OsNIP1;3 (69.9) | OsNIP1;3 (67.8) |
| HvNIP2;1 | NPA/ NPA | G | S | G | R | L | T | A | Y | F | PM/ER | antimony, arsenite, boron 3, silicon 4, urea, water 6 | OsNIP2;1 (84.0) | OsNIP2;1 (78.9) |
| HvNIP2;2 | NPA/ NPA | G | S | G | R | L | T | A | Y | F | PM/Chl | antimony, arsenite, boron, silicon, urea, water 6 | OsNIP2;2 (88.5) | OsNIP2;2 (87.0) |
| HvNIP2;3 | NPA/ NPA | G | S | G | R | L | T | A | Y | F | PM/Chl | antimony, arsenite, boron, silicon, urea | OsNIP2;2 (87.6) | OsNIP2;2 (87.7) |
| HvNIP3;1 | NPS/ NPV | A | I | G | R | F | T | A | Y | L | V | antimony, arsenite, boron | OsNIP3;1 (71.6) | OsNIP3;1 (88.5) |
| HvNIP3;2 | NPA/ NPA | V | I | A | R | Y | T | A | Y | L | PM/ER | - | OsNIP3;3 (55.7) | OsNIP3;3 (58.9) |
| HvNIP4;1 SIPs | NPA/ NPA | C | G | G | R | M | S | A | Y | V | PM | - | OsNIP4;1 (72.2) | OsNIP4;1 (59.8) |
| HvSIP1;1 | NPT/ NPA | L | V | P | N | M | A | A | Y | W | ER | - | OsSIP1;1 (83.0) | OsSIP1;1 (85.0) |
| HvSIP2;1 | NPL/ NPA | S | H | G | S | F | A | A | Y | W | PM/V | - | OsSIP2;1 (83.7) | OsSIP2;1 (74.5) |
‘-’ Indicates no information available.
aPotential substrate transported predicted using the signature sequences developed earlier [31]. The underlined substrates have been experimentally proven for the particular barley AQPs: 1[48], 2[50], 3[49], 4[51], 5[40], 6[26], 7[13], 8[21].
*Only the highest % identity score of each sequence is listed. The identity scores were obtained based on alignments of the cDNAs and putative protein sequences by pairwise identities in BioEdit (S3 Table). The AQPs annotated in this study are shown in bold. Sub-cellular locations: Chl (chloroplast), ER (endoplasmic reticulum), M (mitochondria), PM (plasma membrane) and V (vacuole).